Plastic containers, for example plastic bottles, can have a container body, to whose one longitudinal end can be connected a container neck, which is equipped with at least one pour opening. The container body can have a regular (for example, circular or else essentially square), cross-sectional surface. It can also have an oval cross-section, however. A bottom section can be connected to the other end of the container body. The bottom section can include a container bottom and an edge area that is pulled up on the sides and that turns into the container body.
The plastic container can be produced in an extrusion-blow-molding method from a single-layer or multi-layer plastic hose that can be extruded continuously or intermittently. In this case, a section of the extruded plastic hose can be introduced into the mold cavity of a blow mold tool and inflated by a gas, introduced with overpressure, such as air, into the shape of the mold cavity. The air blast is supplied by a calibrating blow pin, which is run into the plastic hose section that is located in the mold cavity. The formed and cooled plastic container is then removed from the mold (i.e., demolded).
The plastic container can also be produced in a single-stage or multi-stage stretch-blow-molding method. In this case, an elongated preshaped body (preform) can first be produced in an injection-molding or impact-extruding method. The preshaped body is used in another step in the mold cavity of a blow mold tool and inflated by a gas that is introduced with overpressure, such as air, into the shape of the mold cavity. During the inflation process, the preshaped body is, in addition, axially stretched by a run-in elongated mandrel. The plastic container that is finish-stretch-blow-molded and cooled into the shape of the mold cavity is then removed (i.e., demolded) in finished form. A single-stage stretch-blow-molding method is when the further processing of the still hot preshaped body is done directly after the production of the preshaped body. During the two-stage stretch-blow-molding method, the preshaped body that is produced is further processed at a different time and/or place, whereby it must be heated again for the actual stretch-blow-molding process.
In some cases, liquid products are stored in plastic containers under a slight overpressure. This slight overpressure is produced, for example, in that after the plastic container is decanted, it is filled with nitrogen gas. The oxygen is displaced by the nitrogen, which otherwise could lead to an oxidation of the contents and thus could reduce the shelf life of the decanted product. However, even products that outgas during storage can lead to a slight overpressure within the plastic container. This overpressure is, for example, 0.3-0.5 bar and can reach up to 1.5 bar. Because of the overpressure, there is a certain risk that the container body will deform in an uncontrolled manner, for example will curve outward, and will thus diminish the structural safety of the container.
Known plastic containers can have weakened areas in the container body, at which the container body can deform to a limited extent. The container body can be designed with a relatively large wall thickness. Such plastic containers that have deformable sections in the container body can be relatively complex in production. In addition, the deformable sections can often greatly limit the space that is available for labeling the plastic container.
Alternative approaches therefore attempt to counteract a deformation of the container body in that the container bottom is designed with deformable areas that are more or less controlled. For example, container bottoms that are designed like membranes and that have several concentrically arranged areas that are connected in a hinged manner to one another and that are curved inward and can bulge outward because of an increased internal pressure are known. Because this deformation process of the container bottom could diminish the stability of the container, the areas of the container bottom that are connected in a hinged manner to one another are arranged between feet that are made in the edge area of the bottom section. For example, plastic containers with five or more feet are known. Aside from the relatively complex design of its bottom section, the container has a greater height because of the feet, without thus significantly increasing in the inside volume. The feet are designed with a relatively large wall thickness because the weight of the filled container is now distributed on a significantly reduced surface. In contrast, however, the desire exists to further reduce the material requirement for the plastic container for ecological and economic considerations.